ENH: listall doesn't simply use concatenated task lists.

The simplistic "listall" action implementation just uses _list() on the concatenation of active and done task lists. This has the following shortcomings:

- Task numbers shown for archived tasks from done.txt are invalid.
- As the number of done tasks likely greatly outnumbers the number of active tasks, the task number padding is often larger than expected (e.g. 0005 instead of 05).
- Verbose output lists all tasks as originating from TODO, whereas it should differentiate between TODO: and DONE: sources.

The main challenge is to keep processing all tasks through a single pass of _list(), so that there is a single, unified sorting applied to all tasks. A custom AWK script sets all (originally invalid) task numbers from done.txt to "0", meaning "archived task".
The verbose message from _list() is replaced with a custom message that shows the tasks from todo.txt, done.txt, and totals.

Oh, and added tests for the previously untested "listall" action.

tests/t1350-listall.sh

@@ -0,0 +1,150 @@
+#!/bin/sh
+
+test_description='listall functionality
+'
+. ./test-lib.sh
+
+cat > todo.txt <<EOF
+smell the uppercase Roses +flowers @outside
+x 2011-08-08 tend the garden @outside
+notice the sunflowers
+x 2011-12-26 go outside +wakeup
+(A) stop
+EOF
+cat > done.txt <<EOF
+x 2011-12-01 eat breakfast
+x 2011-12-05 smell the coffee +wakeup
+EOF
+
+test_todo_session 'basic listall' <<EOF
+>>> todo.sh -p listall
+5 (A) stop
+3 notice the sunflowers
+1 smell the uppercase Roses +flowers @outside
+2 x 2011-08-08 tend the garden @outside
+0 x 2011-12-01 eat breakfast
+0 x 2011-12-05 smell the coffee +wakeup
+4 x 2011-12-26 go outside +wakeup
+--
+TODO: 5 of 5 tasks shown
+DONE: 2 of 2 tasks shown
+total 7 of 7 tasks shown
+EOF
+
+test_todo_session 'listall highlighting' <<EOF
+>>> todo.sh listall
+5 (A) stop
+3 notice the sunflowers
+1 smell the uppercase Roses +flowers @outside
+2 x 2011-08-08 tend the garden @outside
+0 x 2011-12-01 eat breakfast
+0 x 2011-12-05 smell the coffee +wakeup
+4 x 2011-12-26 go outside +wakeup
+--
+TODO: 5 of 5 tasks shown
+DONE: 2 of 2 tasks shown
+total 7 of 7 tasks shown
+EOF
+
+test_todo_session 'listall nonverbose' <<EOF
+>>> TODOTXT_VERBOSE=0 todo.sh -p listall
+5 (A) stop
+3 notice the sunflowers
+1 smell the uppercase Roses +flowers @outside
+2 x 2011-08-08 tend the garden @outside
+0 x 2011-12-01 eat breakfast
+0 x 2011-12-05 smell the coffee +wakeup
+4 x 2011-12-26 go outside +wakeup
+EOF
+
+test_todo_session 'listall filtering' <<EOF
+>>> todo.sh -p listall @outside
+1 smell the uppercase Roses +flowers @outside
+2 x 2011-08-08 tend the garden @outside
+--
+TODO: 2 of 5 tasks shown
+DONE: 0 of 2 tasks shown
+total 2 of 7 tasks shown
+
+>>> todo.sh -p listall the
+3 notice the sunflowers
+1 smell the uppercase Roses +flowers @outside
+2 x 2011-08-08 tend the garden @outside
+0 x 2011-12-05 smell the coffee +wakeup
+--
+TODO: 3 of 5 tasks shown
+DONE: 1 of 2 tasks shown
+total 4 of 7 tasks shown
+
+>>> todo.sh -p listall breakfast
+0 x 2011-12-01 eat breakfast
+--
+TODO: 0 of 5 tasks shown
+DONE: 1 of 2 tasks shown
+total 1 of 7 tasks shown
+
+>>> todo.sh -p listall doesnotmatch
+--
+TODO: 0 of 5 tasks shown
+DONE: 0 of 2 tasks shown
+total 0 of 7 tasks shown
+EOF
+
+cat >> done.txt <<EOF
+x 2010-01-01 old task 1
+x 2010-01-01 old task 2
+x 2010-01-01 old task 3
+x 2010-01-01 old task 4
+EOF
+test_todo_session 'listall number width' <<EOF
+>>> todo.sh -p listall
+5 (A) stop
+3 notice the sunflowers
+1 smell the uppercase Roses +flowers @outside
+0 x 2010-01-01 old task 1
+0 x 2010-01-01 old task 2
+0 x 2010-01-01 old task 3
+0 x 2010-01-01 old task 4
+2 x 2011-08-08 tend the garden @outside
+0 x 2011-12-01 eat breakfast
+0 x 2011-12-05 smell the coffee +wakeup
+4 x 2011-12-26 go outside +wakeup
+--
+TODO: 5 of 5 tasks shown
+DONE: 6 of 6 tasks shown
+total 11 of 11 tasks shown
+
+>>> TODOTXT_VERBOSE=0 todo.sh add new task 1
+
+>>> TODOTXT_VERBOSE=0 todo.sh add new task 2
+
+>>> TODOTXT_VERBOSE=0 todo.sh add new task 3
+
+>>> TODOTXT_VERBOSE=0 todo.sh add new task 4
+
+>>> TODOTXT_VERBOSE=0 todo.sh add new task 5
+
+>>> todo.sh -p listall
+05 (A) stop
+06 new task 1
+07 new task 2
+08 new task 3
+09 new task 4
+10 new task 5
+03 notice the sunflowers
+01 smell the uppercase Roses +flowers @outside
+00 x 2010-01-01 old task 1
+00 x 2010-01-01 old task 2
+00 x 2010-01-01 old task 3
+00 x 2010-01-01 old task 4
+02 x 2011-08-08 tend the garden @outside
+00 x 2011-12-01 eat breakfast
+00 x 2011-12-05 smell the coffee +wakeup
+04 x 2011-12-26 go outside +wakeup
+--
+TODO: 10 of 10 tasks shown
+DONE: 6 of 6 tasks shown
+total 16 of 16 tasks shown
+EOF
+
+test_done